dhw and ch working at same time.

[alfieralph]

i have recently moved into my first home and inherited a faulty boiler.
ARISTON euro combi SX20 mffice

The DHW flow rate is poor, it takes about 3/4 hr to fill our small bath.
Regardless of the summer switch position the CH will operate at whatever temp the DHW is set at. Therefore in July when it is 30 degrees outside I run a bath, not only does it take ages to fill but the the radiators come on full all over the house and I'm sweltering.
The DHW flow is poor upstairs and downstais, the boiler is located downstairs.
When the summer switch is in the summer position is seems to take longer for the DHW to get warm.
The pressure in the boiler is a satisfactory 1.5 bar.

 

[weargas]

sounds like multiple problems. I would suggest an ariston recommended engineer for this one. You certainly have a diverter valve problem but i suspect you have deeper problems to go with it.

 

[DP]

I get the impression that the boiler has been tempered with for it to behave like this.

 

[weargas]

i got the feeling the dhw flow rate has been reduced to compensate for the heat loss down the ch

 

[DP]

Boiler uses a shunt valve. For HW demand, the valve will have shut the CH port before the microswitch operates to start the boiler.

 

[weargas]

in the sx 20 the dhw diaphragm lifts above the diverter but the diverter section relies on it's own spring to lift like older worcesters(it isn't pushed by the diaphragm). The dhw diphragm may be lifting all the way but the diverter valve beneath may not , resulting in the ch port being left partially open.

 

[DP]

My train of thought was that the poster has moved into a new house. I can imagine the boiler starts misbehaving in HW mode. I have come across diverters where the microswitch had packings inserter to fire the boiler. Weargas I can see where you are coming from as well.

Similarly went to a Gloworm back boiler that had been suffering from constant pilot outage. Unknown dikhead had been into the boiler and bent the thermocouple towards the smaller pilot flame. Had also used rope sealant on both sides of the rope seal making boiler dismantling a little more tricky.

Another one I went to see is a LFE fire installed by a friend of a friend who is a gas engineer. Fire fits the wall leaving large gaps between the wall and firebox flange, fire offset in relation to the hearth (which itself is not bedded in, bottom of the firebox 10mm higher than the hearth abd bare copper used for concealed gas line.

One more. Woman's gas fire suffering from random pilot outage. She gets someone from her local to come round and have a look at the fire. He replaces the (ODS) thermocouple with a universal. Pilot still erratic. She, thinking fire if totally kaput, buys a new fire. On recomendation, I went to see the fire. Removed the fire from the opening to find opening had been reduced with plasterboard. Paper on the plasterboard had burnt away. Advised her to get a builder to reduce the opening and then progress could be made to get the fire working (old or new whatever her choice)

In each case 'engineers' were 'CORGI Registered' but ID cards were not produced.

 

[weargas]

I have come across diverters where the microswitch had packings inserter to fire the boiler.

5p piece glued on top? It's a favourite.